1. Field of the Invention
This invention relates to a battery and an electric double layer capacitor which are packaged in a resin sheet.
2. Description of the Related Art
Recent downsizing and weight reduction of mobile devices in information communication applications have led to intensive attempts to develop smaller and lighter batteries and electric double layer capacitors while being capable of rapid charge/discharge.
For meeting the needs for smaller and lighter batteries and electric double layer capacitors, it has been proposed to use a laminated film composed of a polymer film layer and a metal foil layer as an outer package material. For improving rapid charge/discharge properties, a metal plate made of, for example, copper having a smaller electric resistance is employed as a terminal.
Japanese Laid-open Patent Publication No. 8-83596 has disclosed a thin card battery wherein a closed battery package consisting of laminated films comprises laminated layers of a cathode, a separator and an anode as well as an electrolyte. Such a battery, however, comprises only one basic cell in which a cathode and an anode are oppositely placed via a separator. Thus, an increased voltage requires connecting a plurality of cells in series outside the package, which makes size reduction of a product difficult. Furthermore, when an electrolyte is acidic and a terminal is a metal plate made of, e. g., copper in the battery, an internal resistance is increased probably due to corrosion of the metal terminal plate caused by its contact with the acidic electrolyte.
Japanese Laid-open Patent Publication No. 6-29154 has disclosed an output terminal in an electric double layer capacitor, which acts as an external terminal by being contacted with a polarizable electrode impregnated with a highly corrosive electrolyte. The output terminal has a configuration where a corrosion-resistant conductive sheet covers an outer surface of the metal terminal plate except an external lead. An electric double layer capacitor produced using such a terminal, however, has an increased outer diameter by an increase in a thickness because both sides of the metal terminal plate is covered by the conductive sheet.
Japanese Laid-open Patent Publication No. 4-237109 has disclosed an electric double layer capacitor having a configuration in which a plurality of devices comprising a gasket are laminated and a sheet of current collector is disposed between two devices, and has described that such a configuration may increase a withstand voltage and reduce the number of current collector, resulting in a smaller thickness. Such a configuration, however, still comprises a gasket contributing to a larger outer diameter of a product. Thus, the configuration is insufficiently effective in size reduction.
In Japanese Patent Application No. 2001-103629 (Japanese Laid-open Patent Publication No. 2002-298798), we have proposed a battery and an electric double layer capacitor, in which a metal terminal plate except its lead is sealed by heat sealing between a conductive rubber and an outer laminated material. Such a configuration may be used to prevent corrosion of the metal terminal plate even when the electrolyte is acidic and to reduce a product size because of absence of a gasket. The battery and the electric double layer capacitor, however, have a single basic cell in which a pair of electrodes are oppositely placed via a separator, so that an increased voltage requires connecting a plurality of batteries or capacitors in series outside the closed package. There is, therefore, room for improvement in size reduction of a product for producing a battery or capacitor having a desired voltage or withstand voltage.